Re-saving PNG deletes EXIF

[esv]

In Setting→General→Formats→Write I have all 4 metadata checkmarks ticked/enabled (as far as I understand, this is a common section for all formats, so should also work for PNG)

• Keep EXIF
• Keep IPTC
• Keep XMP
• Keep ICC profile

However, when I resave a scanned PNG file (via export or cropping and saving or saving as), the EXIF section of the file is gone

XnView: MP 1.3.1 64 bit
OS: macOS 10.15.7 64bit (though same thing happens on Windows 10)

[xnview]

EXIF is not supported by PNG

[esv]

Well, it is supported by the PNG:

• it's part of the original file created by the standard macOS scanner app
• from this SO answer https://stackoverflow.com/questions/954 ... a-like-jpg it's part of the PNG spec since 2017 (Version 1.5.0 (July 2017) of the Extensions to the PNG 1.2 Specification)

[xnview]

yes right, i didn't know that a special chunk was added. Could you send me a PNG file with EXIF data?

[esv]

Sure thing, the attached file is a tiny screenshot of a white screen area, it does show IFD0 and Exif IFD fields

[xnview]

See issue for current status and some details.

[xnview]

This problem is supposed to be fixed in XnView MP 1.4.3. Please check and confirm the bug fix here.

[esv]

Upd: I've learned that the Apple chunk is supposed to disappear per PNG spec, but that still doesn't explain the warning

Just converted a screenshot in the new version and noticed that there is a warning from exiftool, though not sure what it is
before

Code: Select all

Apple Data Offsets              : (Binary data 28 bytes, use -b option to extract)

after

Code: Select all

No field 'Apple Data Offsets' (as it should be)
Warning                         : [minor] Text/EXIF chunk(s) found after PNG IDAT (may be ignored by some readers)

[xnview]

could you send me the file?

[esv]

Sure
xn1.png is the original screenshot
xn2_edit.png is the same file cropped in XnViewMP with the warning

[xnview]

it's only a warning, LIBPNG writes at the end the EXIF chunk...